JPS5923512A - Laser marking method for semiconductor wafer - Google Patents

Abstract

PURPOSE:To put a mark without causing any damage on the element forming surface of a wafer by a method wherein laser beams radiate the side face of the wafer to engrave the mark, in case of providing the mark on the semiconductor wafer. CONSTITUTION:A beam L from an oscillator 1, such as a CW excitation, Q- switch Nd:YAG laser or normal pulse oscillation-type Nd:YAG laser, which can oscillate a pulse laser, radiates mirrors 2 and 4 which have a function to deflect the beam L in the directions orthogonal to each other. Then, the mirrors 2 and 4 are deflected by drive parts 3 and 5, respectively, in accordance with a marking character, so that the beam L is condensed through a condensing lens 6 and radiate onto a wafer 7. At this time, the irradiated surface is selected to be the side face of the wafer 7 rather than an element forming surface 8 of the wafer 7. The side face may be of either an orientation flat face 9 or an arcuate face 10, but the face 9 is more preferable for optical reading of the mark.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for marking a semiconductor wafer, and more particularly to a method for marking a semiconductor wafer while maintaining its element formation surface in good condition.

[Technical background of the invention and its problems]

Conventionally, it has been put to practical use to mark loft numbers and the like on semiconductor wafers by evaporating and removing them with a laser beam.

Characters are also engraved by hand using diamond needles. However, these marking processes tend to cause unevenness on the element forming surface of the wafer, that is, when characters are written, foreign matter may adhere to the grooves where the characters are formed.
Material removed from the grooves adheres to the surrounding planar surfaces and substantially changes the thickness of the wafer.

This means that when forming fine patterns on a wafer at high density using a photographic method, the thickness is substantially thicker around the characters, so if the wafer is placed on a flat surface, the surface will be tilted and uniform exposure will not be possible. There are drawbacks such as.

Therefore, after marking with a laser, it was necessary to finish the 9 raised areas around the letters flat by etching or polishing.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for marking a wafer that does not cause problems in the semiconductor manufacturing process even if there is a bulge υ around the wafer during marking.

[Summary of the invention]

In the present invention, the side surface of a semiconductor wafer is irradiated with a laser beam to make a mark, and is designed to be unaffected by changes in the unevenness caused by the marking.

[Embodiments of the invention]

An embodiment of the invention is shown in FIG. (1) is a laser oscillator, and a pulse laser such as a CW excitation Q-switched Nd;YAG laser or a normal pulse oscillation Nd;YAG laser can be used. (2) and (4) are laser beam reflecting mirrors.These mirrors have the function of deflecting the laser beam (L) in mutually orthogonal directions.The deflection angle of the mirrors is determined by an electrically driven galvanometer, etc. A drive unit consisting of (
3) and (5). The laser beam (L) is deflected according to the marking characters by the two reflection plates m(2) and (4), and the beam is directed to the wafer (the surface forming the force element (8) by the condensing lens (6). ), but the side surface is irradiated.This side surface has an orientation flat surface (9) that determines the orientation of the wafer, and a circular arc surface α [9] following this, but both of them are irradiated, but after marking. When reading optically, it is convenient to use the flat surface (9) of the orientating machine as a marking place.The laser may be a CO, Exil laser, or other laser other than Nd; YAG laser. But that's fine.

〔Effect of the invention〕

Marking the sides in the thickness direction has the following advantages.

(a) When irradiating with an L/-f beam, the laser beam can be irradiated horizontally, so that the evaporated matter during engraving (evaporation removal) does not adhere to the surface of the wafer. That is, the evaporated material flies away from the wafer in a direction parallel to the upper and lower surfaces of the wafer, and does not scatter in one direction toward the wafer. Therefore, most of it can be removed by installing a suction device between the laser irradiation lens and the wafer.

(b) The surface on which characters are marked is the surface on which elements are formed (8)
Or, because it is not the back side of the wafer, when it is installed on a flat surface, the height of the surface is parallel to the installation table surface and the thickness of the wafer, and it is not affected by the embossment etc. that occurs during marking. No errors occur when forming high-density patterns.

(c) Condensing lens for marking 7>f Since it is provided horizontally apart from the wafer, evaporated matter does not fall in the direction of the condensing lens.

(2) When characters are to be read in a later process, the marking position is searched from a wide area on the wafer surface, but if the characters are written on the orientation screen flat, searching for the marking position is easy.

(f) Since the marking location is well away from the location of the wafer where the devices are formed, there is little thermal influence on the devices. Therefore, a pulsed laser with a wide pulse width and a large processing capacity can also be used. This allows you to mark the text thickness.

The depth is large and it is easy to tighten and υ.

(f) Since the marking position is on the side, there is no need to flip the semiconductor wafer when reading.

[Brief explanation of the drawing]

The drawing is a perspective view showing an embodiment of the present invention. (L)...Laser light (7)...Semiconductor wafer (9)...Orientation hook)
Ql... Arc surface agent Patent attorney Kensuke Norichika (Haga1
name) 52

Claims (1)

[Claims] A laser marking method for semiconductor wafers that involves irradiating the side surface of a semiconductor wafer with a laser beam to mark it.